The Research On All Optical Signal Processing Based Silicon Microring Resonator

For the last 40 years, the silicon chip has been the mainstay of the electronics industry and has a revolutionary impact on the world. Today, a silicon chip with a size of fingernail contains nearly 1 billion transistors and has the computing power equavilent to that would take up an entire room of servers a decade ago. As the Moore's law continues, and Internet-based communication continues to grow, the bandwidth demands will continue to increase and push the limits of copper-based technologies. These limitations will necessitate optical-based solutions. However, any optical solution must be cost-effiency if it is to be applied to the mass market. Under such circumstance, integrated photonics has been a hot research topic in both the academy and industry.Silicon photonics, which is based on SOI technology, has recently attracted much attention. Recent advances and breakthroughs in silicon photonic device have shown that silicon is a promising platform to build optical integrated devices. Due to the ability to utilize existing CMOS fabrication facilities, silicon photonics could provide low-cost opto-electronic solutions for applications ranging from telecommunications down to chip-to-chip interconnects, and in the future, revolutionize optical communications.My thesis focuses on the system applications of the linear and nonlinear properties of a building block in silicon photonics—silicon microring resonator as follows: Signal processing subsystem based on linear property of silicon microring resonatorSilicon microring resonator is in essence a filter and the amplitude and phase response of the silicon microring resonator is thoroughly investigated in this thesis. We have fabricated silicon microring resonator with different size and demonstrated novel signal processing subsystem in the following three aspects:1) Optically tunable optical delay line: tunable optical delay line is a key technology in the optical packet switching system, where the optical signals are directly buffered to avoid complex O-E-O conversion. Microring resonator can increase the delay time effectively compared with the fiber-based delay line with the same length. In this thesis, we have investigated the delay performance of three important modulation formats (NRZ, RZ, DPSK) for the first time, and realized an optically tunable optical delay using thermal nonlinear effect in silicon.2) Optical processing of microwave signal: silicon microring resonator is suitable to be used in optical processing of microwave signal as its bandwidth is generally in the range of several GHz to several tens of GHz. This thesis proposes for the first time and verifies using experiment that a microring resonator working at the critical coupling condition can function as an optical differentiator; we further demonstrate frequency quadrupling using the proposed optical differentiator; Photonic generation of Ultra-wide-band (UWB) signal based on the silicon microring resonator as a frequency discriminator is also experimentally demonstrated.3) Application of high Q microring resonator in all optical modulation format conversion: We discuss the possibility to realize format conversion from NRZ to PSK using a high Q silicon notch filter and verified the proposal using a stimulated Brillouin scattering (SBS) based narrow band notch filter in fiber. Signal processing subsystem based on free carrier effect in silicon microring resonatorFree carrier can be generated through two photon absorption (TPA) effect in silicon devices with injection of high power laser. Blue shift of the optical spectrum of the silicon microring resonator could be found with the modulation of the refractive index of the silicon due to the change of the carrier density. We proposed two novel applications in the following two aspects based on the carrier effect:1) Wavelength conversion based on silicon microring resonator with mode split: we demonstrate wavelength multicasting based on the mode split microring resonator and further realize all optical format conversion from NRZ to FSK based on the similar principle.2) Application of slow response of the free carrier effect: overshoot can be found at the rising and falling edge of a pulse due to the limited response time of free carrier effect. We propose a simple method to achieve photonic generation of UWB monocycle signal based on this phenomenon.